1. Field of the Invention
The present invention relates to an acoustic wave element and to an electronic device such as a mobile phone.
2. Background Art
Hereinafter, a description is made of a conventional acoustic wave element using FIG. 7. FIG. 7 is a schematic sectional view of a conventional acoustic wave element.
There is known a chip-size package element as shown in FIG. 7 as conventional acoustic wave element 101. Element 101 includes piezoelectric substrate 102 and IDT electrode 103 placed on substrate 102. Insulating body 110 is formed on piezoelectric substrate 102 so as to cover IDT electrode 103. Body 110 protects electrode 103 from the external environment.
This conventional acoustic wave element 101 further includes internal electrode 104, sidewall 105, and lid 107. Internal electrode 104 is placed on piezoelectric substrate 102 and is electrically connected to IDT electrode 103. Internal electrode 104 is made of aluminum for example. Sidewall 105 is provided around IDT electrode 103 on piezoelectric substrate 102. Lid 107 is provided on sidewall 105 so as to cover space 108 above IDT electrode 103 through adhesive layer 106 made of an adhesive.
Examples of prior art documents related to this application include WO/2006/106831.
In the process of manufacturing above-described conventional acoustic wave element 101, lid 107 is bonded onto the top surface of sidewall 105 with an adhesive. This bonding pressure causes the adhesive to protrude from between sidewall 105 and lid 107. A large amount of the adhesive protrusion leads to poor connection between an external electrode (not shown) and internal electrode 104 and causes the adhesive to contact IDT electrode 103. Meanwhile, decreasing the bonding pressure to reduce the protrusion amount of the adhesive reduces the close-contact strength between sidewall 105 and lid 107, which causes a reliability defect in acoustic wave element 101.